Various elastomeric polyurethane compositions useful as adhesives and sealants are available commercially. Generally these compositions comprise uncured natural or synthetic rubbers together with various curing agents and accelerators. Polyurethane adhesives are known and are widely used for bonding various metallic, plastic and glass substrates because of their good strength and versatility. Introduction of a urea linkage to a polyurethane formulation, as in the present invention, improves the adhesion as well as the physical properties. The urea linkage is hydrolylically stable and unaffected by a high concentration of water at elevated temperature. Urea bonds give sufficient cohesive strength, promote adhesion and give higher thermal stability to the polymers.
Japanese Kokai 60/90215 describes polyurethane aqueous dispersion adhesives prepared from a polybutadiene polyol, a diisocyanate, a diol containing .gtoreq.1 tertiary amino group and a quaternization agent to form an emulsion.
U.S. Pat. No. 4,515,933, May 7, 1985 discloses a one-component polyurethane adhesive composition comprising a secondary or tertiary aliphatic diisocyanate pre-polymer, a polyol compound, a chain extender of sucrose and sorbitol and an organometallic curing agent.
Processes for the preparation of the polyhydroxybutadiene employed in the reaactive blend of the instant invention are known in the art, and may be prepared, for example, by the methods described in U.S. Pat. Nos. 3,333,015, 3,673,168 and 3,796,762 all incorporated herein by reference.
The amine terminated polybutadienes employed in the reactive blends of the present invention may be prepared as set forth in the co-pending application Ser. No. 06/748,068 filed June 24, 1985 in the name of Harry R. Hinney and Jamil Baghdadchi entitled Amine Terminated Polybutadiene Compositions and Preparation Thereof, which application is incorporated herein by reference.
It is an object of the present invention to provide a novel two-component polyurea/polyurethane adhesive composition which is heat curable and has excellent adhesive properties.
It is another object to provide a process for bonding substrates with the polyurea/polyurethane adhesive by applying a wet film of adhesive between and in contact with the substrate and curing same at ambient or elevated temperature to form an exceptionally strong bond.
These and other objects and advantages of this invention will become apparent from the description of the invention which follows and from the claims.